Catalysis of Organic..

Marincean et al. 429Experimental SectionThe Ru/C catalyst was provided by PMC, Inc. and consists of 5.0 wt% Ru onactivated carbon support. The Ni/Re/C catalyst comprises 2.5 wt% Ni and 2.5 wt%Re on activated carbon. Both catalysts were characterized via N 2 physisorption andH 2 chemisorption using a Micromeritics ASAP 2010 apparatus; the results arepresented in Table 1.Table 1. Catalyst PropertiesCatalyst BET a Pore Total Pore Micropore Metal Metal Surface(m 2 /g) Diam. a (Å) Vol. a (cm 3 /g) Vol. a (cm 3 /g) Dispersion b (%) Area b (m 2 /g)Ru/C 670 34 0.56 0.17 8.8 1.6Ni/Re 1500 20 0.76 0.35 5.6 1.2a Determined by N 2 physisorption at 78K b Determined by H 2 chemisorption at 308KAll reactions were run in a Parr stirred autoclave (Model 4561) at 1000 psi H 2and 200°C for 6h. A weighed quantity (0.5 g dry basis) of the catalyst, Ru/C orNi/Re/C, was introduced into the reactor and reduced at 250ºC and 200 psi H 2(Ru/C) or at 280 o C and 500 psi H 2 (Ni/Re/C) for 13 hours. After cooling, 100ml ofsolution (1.0M GO and 0.1-1.0M KOH) was added to the closed reactor. Forreactions in solvent mixtures, entries 1-4 in Table 2, the water/solvent ratio was 1/9(v/v). When the solvent was either t-BuOH or 1,4-dioxane, 1.5 g of water was addedto the solution to facilitate dissolution of KOH, because of its low solubility thesesolvents. Once steady state was achieved following heatup, samples were taken at 30minute intervals for the first hour, and then hourly, and analyzed via HPLC. TheHPLC column was a BIORAD Aminex HPX-87H run at 65ºC with 5mM H 2 SO 4 asthe mobile phase at a flow rate of 0.6ml/min, using both UV (210 nm) and refractiveindex (RI) detection.Final quantitative evaluation of feed conversion and product distribution, givenin Tables 2 and 3, were based on HPLC analyses after 6h reaction time for mostreactions. In several cases evaluation is based on the samples taken at 5h. Selectivityis defined as mol product formed/mol glycerol converted; yield is mol productformed/mol initial glycerol. The carbon balance is defined as:C Balance(%)= {[GO] + [PG] + [EG] + [LA]} final / [GO] initial x 100We did not explicitly account for the number of carbon atoms because allcompounds have the same number of carbons except EG. In the case of EG (Scheme1), for each molecule of EG formed there is a corresponding one-carbon compoundformed as well.In reaction, time t = 0 is defined as the point when reaction conditions arereached (200ºC ) and the reaction vessel is pressurized with H 2 . Hence, for thesolvents i-PrOH or t-BuOH there is PG in the reaction mixture at t=0 because ofreaction during the 15 minute heatup. However, it is clear that base is necessary for